This invention relates to marine propulsion devices, such as stern drive units and outboard motors, including a reversing transmission and a shifting mechanism therefor and, more particularly, to marine propulsion devices including means to assist transmission shifting.
Marine propulsion devices such as outboard motors and stern drive units commonly employ reversing clutches or transmissions which connect the output shaft of an engine to the propeller shaft to provide forward drive, reverse drive and neutral operations. Such transmissions frequently include a pair of opposed, axially spaced drive gears and a clutch dog which is splined to the propeller shaft and can be selectively shifted axially into engagement with the drive gears. The shiftable clutch dog has driving lugs which engage complementary driving lugs on the drive gears.
Relatively high shift load can be experienced when attempting to shift the transmission from either forward drive or reverse drive to neutral. The torque exerted on the clutch dog lugs by a drive gear creates a resistance to movement of the clutch dog from an "in gear" position to neutral. Shifting can be facilitated by momentarily interrupting engine operation and thereby minimizing this torque.
Examples of prior arrangements including an electrical control for facilitating transmission shifting are disclosed in the following United States patents:
______________________________________ Patentee U.S. PAT. NO. Issue Date ______________________________________ Elkin 2,297,676 Oct. 6, 1942 Moori et al 3,910,388 Oct. 7, 1975 Leighton et al 4,072,204 Feb. 7, 1978 Long 4,215,596 Aug. 5, 1980 Dretzka et al 4,262,622 April 21, 1981 ______________________________________